In order to avoid congestion and insure adequate traffic flow in packet communication networks, it is common to control the access of packet sources to the network on an ongoing basis. In order to successfully control traffic access, it is necessary, first, to accurately characterize the traffic so as to provide appropriate bandwidth for carrying that traffic. Simple measurements which provide accurate estimates of the bandwidth requirements of a source are taught in the copending application Ser. No. 07/942,873, filed Sep. 10, 1992, U.S. Pat. No. 5,274,625, and assigned to applicants' assignee. In this application, the parameters used to characterize traffic include R, the peak bit rate of the incoming traffic in bits per second, m, the mean bit rate of the incoming traffic in bits per second, and b, the mean burst length of the traffic in bits. Rather than using the actual burst length, however, a so-called "exponential substitution" technique is used to calculate and equivalent burst length which would produce the same packet loss probability if the traffic were a well behaved exponentially distributed on/off process. For traffic widely differing from such an exponential process, this equivalent burst length produces a much more accurate characterization of the actual traffic and therefore permits a higher density of traffic on the same transmission facilities.
The measured parameters are used to control the access of signal sources to the network when the actual traffic behavior departs significantly from the initial assumptions. A leaky bucket mechanism is one technique for controlling access to the network when the traffic exceeds the initial assumptions, but yet permits transparent access to the network when the traffic remains within these initial assumptions. One such leaky bucket mechanism is shown in the copending application Ser. No. 07/943,097, filed Sep. 10, 1992, U.S. Pat. No. 5,311,513, and assigned to applicant's assignee. More particularly, the leaky bucket mechanism of this application prevents saturation of the network by low priority packets by limiting the number of low priority packets which can be transmitted in a fixed period of time while imposing a minimum on the number of red packets transmitted at a given time. Such leaky bucket control mechanisms optimize the low priority throughput of the packet network. High priority traffic, of course, is transmitted with little or no delay in the leaky bucket mechanism.
The above-described mechanisms are suitable for controlling traffic only if the traffic is reasonably well-behaved and remains within the general vicinity of the initially assumed traffic parameters. The traffic management system, however, must be structured to deal with traffic which is not well behaved and which departs substantially from the initially assumed traffic parameters. If such a departure persists for any significant length of time, a new connection bandwidth must be assigned to the connection to accommodate the new traffic parameters. Such adaptation of the control system to radical changes in traffic behavior presents the problems of filtering the traffic measurements to separate transient changes of traffic behavior from longer term changes, and determining reasonable ranges within which the initially assumed traffic parameters can be maintained and outside of which new connection bandwidths must be requested. A bandwidth too large for the actual traffic is wasteful of connection resources while a bandwidth too small results in excessive packet loss. Ancillary problems include reasonable ease in implementation of the adaptation process and reasonable computational requirements in realizing the implementation.